Allotter



Feb. 27, 1945. B. A. WALLACE 2,370,335

ALLOTTER Filed Aug. 3, 1940 5 Sheets-Sheet 1 7375.7 M14. l H2227' Feb.27, 1945. B, A WALLACE 2,370,335

ALLOTTER Filed Aug. 3, 1940 3 Sheets-Sheet 2 /P//VG//V G TONE Fell 27,1945- Y B. WALLACE ALLOTTER Filed Aug. 3, 1940 3 Sheets-Sheet 3 m mmmWML Patented Feb. 27, 1945 UNITED STATES PATENT OFFICE ALLOTTER Bert A.Wallace, Chicago, Ill., assignor to Kellogg Switchboard and SupplyCompany, `Chicago, Ill., a corporation of Illinois Application August 3,1940, Serial No. 350,222

15 Claims. (Cl. 179-18) The present invention relates in general toautomatic telephone systems, and more in particular to automatictelephone systems of the relay type, which connections between callingand called lines are established solely by means of relays. The generalobject of the invention is to provide a new and improved system of thischaracter.

The system disclosed herein is a two-digit system, having a maximumcapacity of one hundred lines. Connections are established bymeans oflink circuits, each link comprising a finder which has access to callinglines and a connector which is directively controlled over a callingline which has been connected with by the .associated nder to completethe connection to the called line. Since the links are provided on a`percentage basis and are common to all the lines, means must be providedfor assigning idle link circuits to calling lines in a systematicmanner, to the end that any calling line may be given theexclusive useof a link circuit to complete the call, so long as idle links areavailable.

A device for assigning link circuits as mentioned in the foregoing iscommonly referred to as an allotter, and a special object of theinvention is tc provide a new and improved allotter, consisting entirelyof relays, and adapted for use in larger systems as well as in the smallsystem disclosed herein.

Other objects and features of the invention will be brought out in thecourse of the ensuing description, reference being made to theaccompanying drawings, Figs. 1, 2, and 3, which show by means of theusual circuit diagrams sufficient of the apparatus and circuits involvedto enable the invention to be explained and understood.

Referring to Fig. l of the drawings, the reference character A indicatesa, subscribers station, which may be of any suitable automatic type,including a dial or calling device. The sub-station A is connected withthe exchange over a line comprising conductors 2 and 3. At the exchangethe line is Provided with the usual line and cut-oli relays 5 and 6.

A second subscribers station is indicated at B and is connected to theexchange'over the line conductors l0 and Il. The line and cut-olf relaysfor the line of station B are indicated at I3 and I4.

As previously mentioned, the maximum capacity of the system is onehundred lines. It is customary, however, to use the digit 0 for callingan operator, which reduces the capacity of the operators equipment isnot shown herein, it may be assumed that the digit 0 is reserved for thepurpose stated and that there .are accordingly only ninety subscriberslines. These lines are divided into nine groups in accordance` with therst or tens digits of their telephone numbers. Thus the lines numberedfrom 1l to 10 constitute the first group, the lines numbered from 21 to20, the second group, and s0 on.

The two lines shown in Fig. 1 are both lines of the first group. Theline of station A is the nrst line of the group, and accordingly thetelephone number is 11. The line of station B is the sixth line of thefirst group, and its telephone number is 16.

Associated with the rst group 0f lines are three control relays 22, 23,and 24. Relay 24 may be referred to as a group control relay and iscommon to all the lines of the group. Relays 224 and 23 may be referredto as subgroup control relays. In explanation of this, it may be statedthat each group of lines is divided into two subgroups, one comprisingthe rst rive lines of the group, and the other the last ve lines of thegroup. Relay 23 is common to lines 11 to 15, constituting the rstsub-group, while relay 22 is common to lines 16 to 10, constituting thesecond sub-group. l

Each of the other groups is provided with a. similar set of controlrelays. The drawings show the group control relay 21 and sub-groupcontrol relays 25 and 2B, which are associated with the ninth group oflines. The group control relays are interconnected by guard circuitswhich are not readily understood from the showing of the rst and lastgroup control relays, and accordingly the drawings also shows the groupcontrol relay of an intermediate group. This is relay 28, associatedwith the second group of lines. Fig. l also shows a iinder whichconstitutes part of one of the link circuits used for establishingconnections. This finder comprises nine tens relays such as relays 3|and 32, five units relays such as 4I and 42, a. switching relay 49, andtwo relays 54 and 551 The tens relay 3| is associated with the rst groupof lines, and is providedwith ten sets of contacts by means of which theten lines of the iirst group may-be connected to a set of tenintermediate trunks. The drawings only show two sets of contacts onrelay 3l, being the sets in which the lines of stations A and B areterminated. The line of station A, vfor example, comprising lineconductors 2 and 3, also the test system to ninety subscribers lines.Although the 55 conductor 4, terminates at the contact set desig- Thedrawings show two of the ten intermediate# trunks above referred to, oneof them being designated by reference numerals 36, 31, and 38. Thesetrunks are multipled to the contact sets of the nine tens relays, asindicated in the drawings, and extend to contact sets on the units re-Ylays. The rst and sixth intermediate trunks extend to the rst unitsrelay 4|, the second and` seventh intermediate trunks extend to the.secv ond units relay 42, and so on.

Each units relay is adapted to extend the two intermediate trunksterminating therein to a pair of intermediate trunks which terminate inthe switching relay 49, one trunk of the pair being the one comprisingconductors 4G, 41, and 48. The intermediate trunk comprising conductors46, 41, and 48 is normallyv connected through contacts of relay 49 tothe trunk line comprising conductors 56, 51, and 53, which leads to theconnector which is ass-ociated with the finder being described. Theotherintermediate trunk of the pair may be connected to the connectortrunk by energization of relay 49.'

Relays 54 and 55 are provided for temporarily connecting up the markingconductors over which the tens and units relays and relay 49 of thefinder are initially energized during the establishment of a connection.

The connector is shown in the lower half of Fig. 2 and in Fig. 3, andcomprises the connector control relays i3 to |22, Fig. 2, the countingrelays 30| to 3|0, Fig. 3, with the two common establish connections tothe ten lines of the .'rstk group and has ten sets of contacts, of whichonly the two sets assigned to the lines of stations A and B are sho-wnin the drawings.

The allotter is shown in the upper half of Fig. 2 and comprises relaysto 2|5. The relays 20| to 2|2 are individual to the link circuits,respectively, relays-M3 and 2|4 are control relays associated with theodd and even individual relays, respectively, while relay 2|5 is acommon control relay. Since twelve individual relays are shown, it willbe understood that twelve link circuits such as the link circuit shownare provided for.. The number may, however, be in-creased or decreasedto suit varying'trac conditions.

The operation of the system will nowbe described, it being assumed forthis purpose that the subscriber at station A desires to call thesubscriber at station B. The connection is established by removing thereceiver at station A and.

When the receiver is removed a bridge is closedacross the lineconductors 2and 3 in known manner and a circuit is completed for theline-relay 5. Upon energizing, relayA 5 grounds the-individual markingconductor `|58 and also grounds conductor 20, which is common to lines 1to 5 of the first group. The grounding of conductor 20 completes acircuit for the group control relay 24 of the rst group which may betraced from ground by way 0f contact 1, conductor 20, contact 60,winding of relay 23, winding of relay 24, contacts controlled at 6|,conductor 62, contact 63, conductor 64, contacts of all intermediategroup control relays such as contact 65 of relay 28, contact 66, andresistance 61 to battery. Relay 24 is energized over the above circuitand locks itself at contact 6|. At contact 66 relay 'i4-.disconnectsbatteryl from conductor 62, which prevents all, the other group controlrelays such as21-and.ZB'rOm'energizing responsive to calls that may beinitiated in other groups. At contact 12 relay 24 places ground on thetens marking conductor 1|, thus preparing for energizing the rst tensrelay such as 3| of the finder in the link circuit to be used.

Thel sub-group controlrelay 23 is'energized in series with relay 24,`and at contact 13 disconnects conductor 2|, common to lines 6 to 0 ofthe rst group, from the sub-group control relay 22, thus preventingrelay 22 from energizing responsive to a call being initiated on one ofthese lines. Relay 23 also connects the ve individual marking conductorssuch as conductor 68 to ve common units marking conductors such as 69.Since conductor 68 is grounded, this operation prepares for energizingtherst units relay such as `4| in the iinder which will be used for thecall.

Attention may now be directed to the allotter which is shown in Fig. 2.The operation of this device will be described in detail later on, butfor the present it will be suflicient to state that one of the relays20|to 2|2 will be in energized p0- sition, thereby assigning theassociated link circuit as the one to be used on the next call. It maybe assumed that the rst link'circuit, the one shown in the drawing, isidle and is the next one t0 be used. Accordingly, relay 20| of theallotter will Ibe in energized position, as shown.

Returning now to the call under consideration, when the group controlrelay 24 energizes it grounds th'e common conductor 15 at contact 14',"thereby establishing a circuit for relays 54 and 55 which may be tracedover said conductor 15 to Contact 2|6 of relay 2|5 and thence by Way ofcontact 2|9 of relay 20|, conductor 16 (individual to the rst linkcircuit), and windings of relays 54 and 55r to battery. Upon energizing,relays 54-and 55A connect the common marking conductors through -to thetens and units relays of the iinderl of the rst link circuit.

.As the result of the extension of the marking conductors, asdescribedinthe preceding paragraph, the tens relayi3| isenergized over the tensmarking conductor 1|, and-the units relay 4| is energized` over theunits marking conductor 69. These relays prepare locking circuits forthemselves at contacts `39 and 11, respectively;` Relay 4| alsodisconnects battery from the other four units relays such as-42 atcontact 18, thereby preventing anyof these other units relays fromenergizing in case one of the lines 12 to15 of the rst; group is callingat this time.

The energization of relays 3| and 4| extends the line of station A tothe line relay in the connector ofthe rst link 'circuit over a' pathwhich includes-contactsV 33 -and,34 `of relay 3|, intermediate trunkconductors 36` andv31, contacts 43 and 44-of relay 4| conductors 40and'41, normally closed contacts of re1ay'49, trunk conductors 56 and51, and the upper and lower windings of the line relay |2|, thesewindings being connected to ground and battery, respectively. The linerelay |2| is accordingly energized, and at contact |26 closes a circuitfor the slow acting release re-` lay |22.

Upon energizing, relay |22 grounds the local holding conductor |45 atcontact |24 and also places ground on the holding conductor 58 of theincoming trunk from the inder. The grounding ofy conductor 58 extendsground over conductor 58' to complete the previously prepared lockingcircuits for relays 3|y and 4|. A circuit for the cut-off relay 6 isalso completed, said circuit extending from the grounded holdingconductor 58 by way of normally closed contacts of relay 49, conductor48, contact 45 of relay 4|, conductor 38, contact 35 o-f relay 3|,conductor 4, and winding of cut-oli relay 6 to battery. On energizing,relay 6 disconnects the line conductors 2 and 3 from ground and from theline relay 5, respectively, which causes the line relay to deenergize.The deenergization of the line relay breaks the circuit of relays 23 and24, and these relays accordingly deenergize also. Ground on conductor 4is also extended over conductorS to the connectors, whereby the line ofstation A is made busy to incoming calls.

When the release relay |22 energizes, it opens its contact |23 and thusdisconnects battery from the conductor 25| leading to the allotter,thereby bringing about certain operations in the allotter, including thetemporary energization of relay 2|5, the deenergization of relay 20|,and the energization of another relay such as 202 in order to assignanother link circuit for the next calling line. These operations will bedescribed presently, but for the moment it will be suflicient to notethat the circuit of relays 54 and 55 is broken at contact 2|6 of relay2|5 and also at contact 2|9 of relay 20|. Relays 54 and 55 accordinglydeenergize and disconnect the marking conductors from the iinder of thefirst link circuit. It will be noted that the circuit of relays 54and'55 is broken at the allotter, even though the group control relay 24may remain energized due to another call and thus maintain ground on thecommon conductor 15.

As the result of all the foregoing, the calling line has been extendedto the connector, where the line and release relays |2| and |22 areenergized. A connection may now be traced from the dial tone source byway of conductor |46, contact |41, contact |39, impedance |48, condenser|49, contact |33, contact |29, and condenser |8|, to the trunk conductory56, whereby a dial tone signal is transmitted to the calling station A,notifying the calling subscriber that dialling oi the called number maybegin. The number of the called subscriber is 16, and therefore the dialis rst operated in accordance with the digit 1.

When the rst digit is dialled, a single interruption is produced in theline circuit and the line relay |2| is deenergized momentarily a singletime. The release relay |22 does not fall back when its circuit isbroken momentarily, due to its slow releasing characteristic. Ondeenergizing, the line relay transmits an impulse to the slow actingrelay ||4 over a path extending from ground by way of contactL |26,contact |25, contact |31, contact |42, conductor |65, and winding ofrelay ||4 to battery. On energizing, relay ||4 When the line relay |2|falls back momentarily, I

it also sends an impulse to the rst counting'relay 30 Fig. 3, over apath which extends from ground by way of contact |26, contact |25,contacts |31 and |42, conductor |61, contact SI5, winding of relay 30|,and through the serially related chain contacts on relays 302 to 3|0,inclusive, to battery. On energizing, relay 30| prepares a circuit forcounting relay 302 at contact 3|8, and closes a locking circuit foritself at contact 311 which extends from the grounded holding conductor|45 by way of contact |64, conductor |10, contact 3H, winding of relay3| winding of relay 30|, and the chain contacts of relays 302 to 3|0,inclusive, to battery. This locking circuit includes relayl 3| l but isineiective to energize said relay until the impulse from the line relayhas terminated, whereupon relay 3| energizes. Relay 3H breaks 'theinitial energizing circuit of relay 30| at contact 3|5 and furtherprepares the circuit of relay 302 at contact 3 6. As the digit l wasdialled, only the counting relay 30| is energized at this time, but theAdescription of the call will not be interrupted, since an opportunityof completing explanation of the operation of the counting chain will beaffordedwhen the results following the dialling of the second digit arediscussed.-

A short interval after the line relay has come to rest after thedialling of the rst digit, the slow acting relay ||4 falls back,followed by relay ||5. The function performed by relay ||5 duringdialling is to prevent two subscribers lines from being momentarilyconnected during thel operationv of the counting relays. It performsthis function by disconnecting the talking conductors |13 and |68 fromtheir branches |14 and |69, respectively, at contacts |55 and |58. Thisoperation is, of course, unnecessary when the digit dialled is the digitl, but is essential on other digits because each counting relay exceptthe i'lrst is energized before the preceding relay is deenergized, aswill appear from the subsequent description.

Continuing Awith the call, when relay ||4 deenergizes, it places groundon the two marking conductors |1l and |12 and completes a circuit forthe first tens relay 32|, the circuit extending from ground on conductor|45 by way of contact IBI, resistance |80, contact |62, conductor |1|,contact 3|9 on relay 30|', and winding of relay 32| to battery. Onenergizing, relay 32| locks itself over a circuit extending from groundon conductor |45, winding of relay H3, conductor |15, lower contact ofrelay 32|, and winding oi" relay 32| to battery. In energized position,the tens relay 32| extends connections from contacts of the ten countingrelays to the ten lines of the rst group.

Relay ||3 is energized in series with relay 32| and at contacts |62 and|63 disconnects the two marking conductors |1| and |12. These conductorsare separated at this time to prevent the false operation of anothertens relay when the next digit is dialled. Relay ||3 also disconnectsground from conductor |10, thereby bringing about the deenergization ofrelays 3H and 30|.

The calling subscriber may now dial the second digit of the callednumber. The second digit is the digit 6, and accordingly a series of sixinterruptions is produced in the line circuit, causing the line relay12| to momentarily deenergize six times. At each deenergization the linerelay sends an impulse to relay ||4, which energizes and remains inoperated positionl duringetheee ries of impulses. Relay is alsovenergizedras. before. When relayvr |I4j enex'gizes,` itrepla'ces groundon conductor |-at'contactll6lgrtherebyt' promptly preparing the; lockingcircuit foruthe!` rst counting relay 30|'. Relay: I`I4falso closes: acircuit for relay I I6,y extending-fromfground bnl. conductor |45 byway. of contact |64,` contact. |60, and Winding of'relay H612 tobattery. On. energizing, relay ||6 locksfitself'atcontact |5'|;.. and atcontact I52fp`1aces' ground-0n" conductor |10 independentof` the contactonr relay I=|4i in'. order that conductor |10' may' bel malntalned`grounded after relay I |4 has deenergized.v Relay` ||6 also disconnectsdial-tone from" the calling line at contact |41. l

While the line relay issending impulses-to -re'- lay I|4, it alsosends-impulses to the counting' relays. The rst impulseenergizes relay301i over a circuit which includes conductorV |61-, con

tacts of relays 302 to 3|0, inclusive, to battery;

On energizing, relay preparesa' circuiti'cr'A relay 302 at contact 3 I8,and locks itself at' con; tact 3I1 over a previously traced circuitwhich includes conductor |10 and relay 3| thelatter relay energizing atthe termination of theilrst impulse. Relay 3|I disconnects the'ir'npulsecon'L ductor |61 from relay 30| and other. odd'A` counting relays atcontact 3| 5, and at'co'ntact'3l Giurther prepares 4the circuit ofrelay302.

On receipt of the second 'impulsefrom the line relay, the secondcounting relay- 302" en'ergizesv over a circuit extending over'conductor ltT'and by way of contact 3I3, winding of-relay'302, con;tact 3|8, contact 3I6, and resistance`330' to battery.' On energizing,relay"302"'lock`s lts'elf in' a new circuit which extends fromgro'unded'conductor |10 by way of Contact 733|, winding of re'- lay 3|2,Winding of relay 302, contact 333;. and" chain contacts on relays` 303'to 3|0, inclusive; to battery. In addition; relay 302" partly pre' paresa circuit for relay 303 at contactv 332' and' breaks the locking circuito'f relays`30`| and 3| I"` at the chain contacts associated' .withcontact aecomoer'gized. responsivetoz the last impulse andv locks.itselfinseries with relay 3|2 at contacts 33.1y and1333,.relay 3|2energizing at the termination of theA impulse. The operation of relay306 selects the sixth line in the group of ten lines that Relayyhas-.been selected` by4 the tens relay 32|. 32| is the rst tens relay.and accordinglyline 16., or the line4 of station B, hasbeen selected.

thetest relayA I |1, normally closed contacts asso'- ciatedwithcontact|40; contact |50, contact |59, contactll34; conductor |66;serially'related con- .tacts ofl relays-3|0, 309; 308, and 301, contact339, conductor- 344', contact 341, conductor' I8,

and thenceitofthe test conductor` I2 of the called:

line', Fig. l. Relay III-also breaks the circuit of relay II5; but relay|5is slow to deenergizefandl eholds' uplongf enough for the called lineto beV tested 'over the circuit described.

Assuming that'the'called line is busy, there will be a ground potentialon conductor |2` and the test relay |I1 in the connector will energize,locking itself atzcontact,` |40. At contact |42 relay ||1 breaks4 theimpulsing circuit, and at contacts. |4| and |43" it' breaks the circuitsof relays IIB' and? ||9,' respectively, preventing these relays fromenergizing when relay I I5? falls' back. Finally, at contact |30, relayI |1 connects a source Yof busy signalling current with the callingline; thus giving the calling subscriber a busy signal. The. callingsubscriber will then replace his receiverLand the equipment in use willbe restored to normal in a manner to be :presently described.

333, whereupon these tworelays'deenergize; 'Rev lay 3.|2 energizesinseries with relay 302 at the" termination of the Second' impulse,disconnects' the' impulse conductor |61l from" relay'` 302 andl othereven counting relays atcontact 3|3 and completes the preparation of thecircuit" of re'- lay4 303 at contact 3I4.

In response to the third impulse relay'30'3en`- ergizes over a circuitvextending over conductor" |61 and by way of contactj 3|5', windingofrelay' 303, contact 332, contact 3|4, andresistan'ce 330 to battery.Relay 303 locks itself over a circuit extending from' the' groundedconductor' |10'by way of contact 334, winding of relay 3H', Winding ofrelay 303, contact 336, and chain contacts of relays 304 to 310,`inclusive, to battery'. Relay 303 also prepares the circuit of relay304" at con*- tact 335, and breaks the circuit ofV relays 302anjd 3|2 at336 by disconnecting theserelays" from the chain circuit to battery.'vRelays 302" and 3'I2` explanation, and need not be describedl in" detail; It will suffice to say that relay 3061s en= Assumingnow that thecalled line is idle, there will'be no ground potential on the testconductor I2 'when' the'test, circuit is completed by the deenergization'ofv relay ||4', and the test relay ||1 will'not beenergized. When relay I l5V falls back,

therefore, a circuit will be' completed for relayv |I8, extending fromgrounded conductorY |45, contact I6|, contact |56, contact |53, contact|411, and winding'of relay ||8 'to battery. On energizing, relay. ||8disconnects'the test circuitI from the test relay ||1 and connects it toground' at contact |34; therebyv grounding conductors I8 and". |2ftomake the calledline busy and completing' a circuit-l for the cut-offrelay I4. Onfenergizing, relay? I4 clears the called line of itslnormalbatteryI and ground connections.

In additiony tothe foregoing, relay I|1 breaks` the impulsing circuit atcontact |31, and at contact. |3511; opens another point in the circuitover' which battery is normally applied to the conducy torl 25|extending to thev allotter. Finally, atv contacts. |33 and |38 relay ||8completes the connection4 to thecalled line, said connection ex-Ytending frornthe incoming trunk conductors 56- and. 51, by way of thecondensers I8| and |82;

contacts IZSand |32 of relay I|9, contacts |33 and |38, conductors |13-and |68, contacts 340 and' 34|, conductors 342 and 343, contacts 345 and346and conductors |6 and |1 to lineconductors I 0' and' ofthe calledline.y

The ringingl interrupter machine connects groundl intermittently to. theconductor |83, thereby operating the ringing relay- IIS at intervalsovera circuit extending over said conductor |83'an'dby way of contact|51, contact |54,.con tact |43, and winding of relay I9 to battery. Onenergizing, relay I |51l breaks the connection tothe called line and'.connects the called line to the ringing. current' generator overconductors I|l4` and |85, therebyrlnging the bell at the called station.At the same time a source of ringing tone signalling current isconnected to the calling line by way of conductor |88 and contact |28,

thereby notifying the calling subscriber that the ringing operation isproceeding. It should be noted also that each time relay ||9 deenergizesit momentarily connects ground and battery to the called line atcontacts |38 and |3|. These contacts should break later than the ringingcontacts |25 and |32, and are eective to dissipate the charge on theline and in the condenser at the called station that may remain afterthe ringing circuit is broken. The object of this operation is toprevent a false operation of the back bridge relay |20.

When the called subscriber answers, the back bridge relay |28 isenergized over the called line in an obvious manner. Relay |28 willenergize at once if the receiver at the called station is removed duringan interval between ringing periods, or as soon as relay ||9 deenergizesii the receiver is removed while the bell is ringing. On energizing,relay |20 closes a circuit for the test relay ||1 at contact |21. Onenergizing, relay H1 functions as a ring cut-off relay, breaking thecircuit of the ringing relay ||9 at contact |43. Relay l1 also breaksthe initial energizing circuit of relay HB at contact |4| but closesanother circuit `for said relay including its locking contact |36 beforeit can deenergize.

The connection between the calling and called lines is now complete andconversation can proceed. The talking circuit includes the condensers|8| and |82. Current for the transmitter at the calling station A issupplied through the windings of the line relay |2| while thetransmitter at the called station B is supplied through the windings ofthe back bridge relay |28.

When the conversation is finished the subscribers will replace theirreceivers and the connection is released. The circuits are so arrangedthat the calling subscriber controls the release of the finder while therelease of the connector is controlled by either the calling or thecalled subscriber, depending on which subscriber last replaces hisreceiver.

When the receiver is replaced at the calling station A the circuit ofthe line relay |2| is bro-ken and said relay deenergizes, breaking thecircuit of the release relay |22. After a brief interval relay |22deenergizes and removes ground from the holding conductor 58, therebypermitting relays 3| and 4| to deenergize. This restores the finder tonormal. The removal'of ground from conductor 58 also opens the circuitof the cut-off relay 6, which. deenergizes and re-connects the lineconductors 2 and 3 to ground and to the line relay 5, respectively, thusplacing the line of station A in normal condition.

At the connector the back bridge relay |28 remains energized until thecalled subscriber hangs up and maintains ground on the holding conductor|45 by way of contact |21 and the locking contact |40 of relay H1; Relay||8 maintains battery disconnected from conductor 25| after relay |22has restored in order to maintain the link in unselectable condition atthe allotter.

When the receiver is replaced at the called station B, relay |20 fallsback and breaks the cir- Thev Accordingly, relays H3, H6, H8, 30B, 3|2,

the test conductor of the called line and the cutoff relay |4 isdeenergized, thereby placing the called line in normal condition.

The connection described in the foregoing is typical of connectionsestablished by calling lines 1 to 5 in all groups. Calls'made by lines 6to 0 in the various groups are the same, except that relay 49 of thender in use is energized on such calls. For example, if an outgoing callis made from the line of station B, which is the sixth line in the iirstgroup, the operation of line relay |3 grounds conductor 2|, and thesub-group control relay 22 is energized instead of sub-group controlrelay 23. Then when relay is energized, assuming that the rst linkcircuit is used for the call, a circuit is completed for relay 49 at thesame time that the circuits are completed for relays 3| and 4|. Relay 4Senergizes and the line of station B, line 16, is connected to theconnector trunk instead of the line of station A. It will be noted thatwhenever relay 49 is energized it becomes locked to the holdingconductor 58' at contact 18. l

Reference Will now be made to Fig. 2 for a more detailed explanation ofthe allotter. From what has been said before it will be understood thatconductor 15 incoming to the allotter is common to all the subscriberslines and may be grounded by any calling line. Also, conductors 16 and25| outgoing from the allotter are individual to the rst link circuit,conductor 16 extending to the finder and conductor 25| extendingv to theconnector. The allotter is provided with as many pairs of outgoingconductors as there are link circuits.l Thus conductors 242, 243, and244 extend to the finders in the second, third, and fourth linkcircuits, and there are eight similar conductors which extend to thefinders in the other eight link circuits. Conductors 252, 253,'and 254extend to the connectors in the second, third, and fourth link circuits,and there are eight similar conductors extending to the connectors inthe other eight link circuits. The conductors such as 16, 242, etc., arecontrol conductors over which the relays such as 54 and 55 are energizedto connect the marking conductors to the finders, while conudctors 25|,252, etc., are test conductors by means of which the allotter determineswhether the link circuits are busy or idle.

One of the relays 20| to 2|2, inclusive, of the allotter is normallyenergized, and for convenience it has been assumed that Athe energizedreand the rst link vcircuit is thus assigned for use on the next call. f

When the next call is made, conductor 15 is groundedin the manneralready explained, andA relays 54 and 55 are energized over conductors15 and 15, whereby the marking conductors are connected up and the nderof the first link circuit is operated to connect with the calling line.The line and release relays of the connector are then operated and thelatter relay opens at contact |23 the previously traced .circuit ofrelay 20| 13o-battery through'resistancet". This-operation'removesthe-:shunt Tfrom vrelay 2|3 and said relay energizes ineseries'i withLrelay" 20 I.

AOn energizing, relay `f2|3 A'closes :a circuit for relay `2 I5, lwhichenergizes .f and vopens conductor I5` at contact 2|6. 'Relay 2 I3 also4closes acircuit for relay i202 extending `from l ground by lway Yoicontact-2|?, contact22I, winding of relay202, andl conductor "252 tobattery in" the' connectorl of the second linkcircuit,=assumingfthat'thislink circuit is idle. On-energizing, relay202closes a locking circuit-for itself'atfcontact221, prepares a circuitfor relay'203'at contact-228, and 'connects-uprelay '2 4 at contact5229. Re1ay'f2 I 4 is shunted by the circuit to Vbattery overvconlductor:2521 and is'not'operated. Relay 202 'also breaks the circuit ofrelays-20| and S2 |13 iatits chain contactscontrolled by contact' 221.'and said relays are "deenergized, theilatter relay breaking thecircuit'of relay 2I5. 'Relay- 2I5=`shouldfbeslow 'to deenergize inorderto aiordf'ample 'time for the operation of theallotterbetweenfsuccessive calls. When relay 2I5 falls back, itiextendsthe vcommon conductor`i by way of contact' 2 |46, con- 'tact 2|'9 of thenow deenergized relay 120| and r"contact 226 of the'energizedAre1ay2'2II2,fto'con ductor'242. `The latter conductorextends tore-`lays such as 54 and '355 in" the Afiinder of the 1second` link circuit,which .is therefore fassigned' for luse on the next call.

When the nextcall is'made,'battery is 'removed from rconductorf252in'the 4connector of :theisecond vlink circuit and relay 12H'-isfenergized yin series vwith relay i202. On energizing, relay 3'2I'4closes :a circuit "for relayIS, which operates againandopensconductor`'5. 'Relay 112|'4 ialso Vcloses/a circuit for-relay203-'Assumingithat the thirdf link circuit is busy, 'there wllllbe''no'battery potential on conductor253'in 'the connector, and thelcircuit 'of relay"`203wvill extend: from ground by 'way ofcontactf2I-8, lcontact-"228,f-vvinding of relay 203, normally `closedcontacts :associated `with -contact 1233, andf'the resistance P238 fto`battery. On energizing, relay `203flocks 'itselff-at contact 23| andatthelassociated chain 'contacts'breaks the circuit of vrelaysl'202 A and"214, which A deenergize. 'Relay 203 'preparesfacircuit 'for relay 204at contact 232, and atfcontact'2i33it=substitutes relay 2 |-3 fortheresistance5238.

Relay 2|3 accordingly energizes in series-with -relay 203 and closeslanothercircuit for relay'e2l5, thus maintaining this relay energized.Relay? 2 |13 also closesv a vcircuit for relay 204 `which extends fromground'by 'way' of contact "2 i1, vlcontact '232, winding of relay'204,l and conductorf254 (assuming that the fourth link `circuit is;idle) Lto battery in the connector `of the 'fourth-link circuit. 'Onenergizing, relayl204 locksitself at contact 235 and atthe lassociatedchain contacts breaksthe 'circuit of relays 203 and`2I-3,' whichdeenergize.

Relay 204 also prepares'a circuitfor relay '-205 at contact 235,-and "atcontact 23T it connects up relay 2|4, Whichdoes not -'energizefhowevenbecause' it` is-shunted by the circuit'over conductor 254'to batteryat'the connector.

AFollowing the deenergization of'relay2 I 3,`1elay 2 I5 isdeenergizedfand 'thecommon'conductor l5 is extended 'byway'of contact2I6, Vand contacts `2|!I, 226, 230, and 234,"tc conductor 244. "The'lattericonductor isindividualtothe fourth link Acircuit which isthus'assigned for use on' thenext call.

In response to `succeeding callsyrelays' 205 to `i2 I2," inclusive; willbe :energized successively in a Vmanner which willbe readily understood`from'the preceding explanation. When relay 2|2 is ener-`g'ized,iitxlor'sksitself at contact :265 and at the @associatedcontactsbreaksthe circuitlof relays 12H fand 2l3.

The-locking circuit of relay 2I2 Vextends vfrom groundfby way of contact265, conductor 26B, contacts controlled at contact 220 of .relay 20|,conductor261, winding of relay. 2I2,

and conductor 262 to battery at the connector in -the twelfthlinkcircuit, assuming that this link circuit is idle.

When the twelfth link circuit is takeninto use,

yrelay 2|4 `energizes in series Withrelay 2I2 and closes a'circuit forrelay 20|, extending from :ground by way of `contactr2l, contact "284,chain sgize. l-'telay l2I2 breaks the locking circuit of 'relay E20 I atvcontact 265, Vand yalso breaks the `initial energizing circuit of thisrelay at contact 264, but at thefsame time it replaces ground on thechainz circuit and thus establishes the previously traced Vcircuit overwhich relay'i20|.is.maintained energizedfwhile the first link circuit iswaiting for afcall.

It will be seen'fromthe' foregoing that the link .circuits lareztestedand assigned for` use by the allotter inzreguiar vrotation, therebyequalizing the'trafiic .between the! link circuits. :the link `.circuitsbecomebusy, rthe allotter will :operate continuously, testing the linkcircuits one In case all after the .'otherluntil'onefof them is'ioundidle `and is "assigned for the next call. During such testing operationftherrelay -'2I5 is 'maintained -energized and' is `only permitted todeenergize Y-aiterianidle llink 'circuit has been vfound andfassignedifor use.

It'will :bei'seen further that fno' link circuit can ybeiassigne'dunless'there isfa'batterypotential on its :associated test conductor."In case a concalls-will itest busy to' the allotter= andlwill not beaassignedffor useby callinglines until the'fuseis replaced.

The testing arrangement'alsolends itself with Ifacility to .the articialVhusying of'the link cir- -cuits.

Each of vthe test `conductors 'such `as '25 I, 252,.etc., is preferablyprovided with a'busykey In the explanationof' the setting up oi aconfnection" from station Af to station B the allotter lwas described'asbeing operated to test-for another link circuit when theline relay wasoperatedover the calling line, the line relay operating o5 "relay I 22and the latterrelayremoving 'connector 'may be considered as'the normaloperation of the `batteryfrom conductori25 I 'at contact |23. Thissystem. However, it is usually desirable as a aftemporary'bridge isclosed across the vtrunk 'conductors 56 and5'I when v'relay 55energizes. 'The closure Aof this bridge insures the energization of thelineand'release relays of the connector even though there'may be adefective contact `at'one vofthe-relays in the iinder, which wouldprevent the line relay in the connector from energizing over the callingline. The possibility of such a case of trouble is remote, but if it didoccur it would tie up the system ,until the calling subscriber replacedhis receiver. The arrangement described prevents such result by insuringthe operation of the allotter regardless of whether the calling line isproperly extended through to the connector or not.

The invention having been described, that which is believed to be newand for which the protection of Letters Patent is desired will bepointed out in the appended claims. i

What is claimed is:

l. In an automatic telephone system, a plurality of connectors, anallotter for assigning said connectors to successive calls, relays insaid allotter, individual test conductors extending from the allotterrelays to the respective connectors, means in each connector formaintaining a potential on its test conductor while the connector isidle, circuits for the allotter relays whereby one of the relays is heldenergized by the idle potential on its associated test conductor, meansin each connector controlled by thecalling subscriber when the connectoris taken into use for a call to remove the potential from said testconductor, and means controlled by the called subscriber for replacingthe potential on said test conductor.

2. The combination, with a plurality of links, of an allotter comprisinga plurality of link selecting, relays, two control relays, means forenergizing said selecting relays successively in search of an idle link,circuits for the odd and even selecting relays including said controlrelays, respectively, whereby said control relays are energizedalternately during the searching operation, link assignment circuitscontrolled by said selecting relays and including a common conductor,and means controlled by said control relays for holding said conductoropen during the searching operation. l

3. In an automatic telephone system, a plurality of link circuits, anallotter comprising a like plurality of link selecting relays, testconductors extending between the selecting relays and their respectivelyassociated links, circuit arrangements whereby one of said relays isnormally maintained in energized condition over its associated testconductor, and a circuit prepared by the energized relay for allottingthe associated link to the next call.

4. The combination, with a plurality of links, of an allotter comprisinga plurality ,of link selecting relays, means local to the allotter forenergizing said relays successively to search for an idle link circuit,and means for preventing the energization of each relay, said meanscomprising a conductor individual to the preceding relay to which apotential is applied at the associated link if the link is idle.

5. The combination, with a plurality of links, of an allotter comprisinga plurality of link selecting relays, means for energizing said relayssuccessively to search for an idle link, said means including twocontrol relays common to the odd and even selecting relays,respectively, and shunt circuits including conductors individual to thelinks for preventing the energization of the associated control relaywhen an odd or even selecting relay iinds an idle link.

6. In an allotter, a series oi selecting relays, a series of testconductors, one for each relay, a normal energizing circuitfor eachrelay includlill ing its test conductor,l an auxiliary energizingcircuit for each relay which is effective in case the normal energizingcircuit is inoperative, two relays which are common to the odd and evenselecting relays, respectively, for controlling said energizingcircuits, and circuit connections for controlling said common relaysover said test conductors.

7. The combination, with a plurality of link circuits, of an allottercomprising a like plurality of link selecting relays, test conductorsextending between said selecting relays and their respective links,means in each link for maintaining a potential on its associated testconductor While the link is idle, local means in the allotter forenergizing said relays successively in search of an idle link until arelay associated with an idle link is energized, a circuit for the lastenergized relay including its associated test conductor, and aconnection to said test conductor which prevents saidlocal energizingmeans from operating the next selecting relay until the potential onsaid test conductor is removed.

8. rlhe combination, with a plurality of link circuits, of an allottercomprising a relay individualv to each link circuit, a normal energizingcircuitl for each relay including a conductor individual to the-associated link, a common energizing circuit for said relays includinga resistance, a locking circuit for the odd relays including a controlrelay for the even relays, and a locking circuit for the even relaysincluding a control relay for the odd relays.

9. The combination, with a plurality of link circuits, of an allottercomprising a like plurality of link selecting relays, means forenergizing each relay over a conductor individual to the associated linkif the link is idle, a common circuit for energizing any relay when itsassociated link is busy, two control circuits common to the odd and evenrelays, respectively, contacts on each relay for disconnecting it fromsaid common circuit and for connecting it to one of said controlcircuits, and relays in said control circuits for controlling saidenergizing circuits.

10. The combination, with a plurality of links, of an allottercomprising a selecting relay individual to each link, means forenergizingy one of said relays over a circuit extending to theassociated link, whereby the associated link is selected for the nextcall, means in the said selected link for opening said circuit when thelink is taken into use, a relay energized in series with the energizedselecting relay responsive to the opening of said circuit, and a circuitfor the next selecting relay controlled by said last mentioned relay.

1l. The combination, with a plurality of links` of an allottercomprising a like plurality of relays, a circuit for energizing a firstone of said relays including a branch local to the allotter and aparallel branch which is open if the associated link is busy, means forclosing said cir cuit to energize the said first relay over both saidbranches or the local branch alone, a third branch of said circuit whichis substituted for said local branch upon energization of said rstrelay, a control relay in said third branch energized in series withsaid first relay in case said parallel branch is open, and a circuit forthe second of said plurality of relays closed by said control relay.

12. In an automatic telephone system, a plurality of link circuits, eachcomprising a relay type finder and a connector, marking conducv-tors, -arelay: individual to-.;each..link circuit4 Afor connecting-said markingconductors to itsinder, a common operating conductor for said individ-.ual relays, yan allotter, relays in-said allotter controlled from saidconnectors,circuits Whereby'one like plurality of link selectingrelays,.test con-- :duotors extendingk between the said selecting-relays andtheir respectively associated link circuits, means including the testconductor of .an

idle link circuit for maintainingthe correspond- .ing selecting `relayenergized. a circuitprepared 20 by the energized selecting relayvforallotting-...the associated link circuit to the next call, and meansresponsive to the -seizure of such link circuit on the next call forsuccessively `energizing the other selectingV relays untila-selectingrelay associated with another idle link circuit isv energized.

114.2In an :automatic telephone system, eplurality of link circuits, .anallottercomprislng'a :like yplurality of linkselecting relays, vmeansfor,maintaining a random one of said relays ener- .g'ized to assign theassociated link circuit to the vnext call, and Imeans responsive tosaidr callin case'the assigned link circuit is the only idle linkcircuit for successively energizing all said selecting relays in searchof an idle linkcircuit.

15.1In lan automatic telephone system, a plurality of link circuits, anallotter comprising-a like plurality of link selecting relays, testconductors extending from said selecting relays to their respectiveassociated link circuits, means in .each link circuit for maintaining atest potential '.onitslassociated test conductor-when theiink circuit.is'idle, Ameans responsive to -a .call for operating 4a plurality ofsaid relays successively to pass :by busylink circuitscharacterized bythe absence-'of potentials on their test conductors, theoperationcontinuing until a selecting relay corresponding to an idle link circuitlisv energized,

and .a -switch vindividual to each link circuit for Aopening its testconductorto make the link cir- 25 cuit busy.

BERT AfWALLACE.

